The present invention relates generally to construction of gas turbine engine integrally bladed rotors and, more specifically, to inertia welding of blades to gas turbine engine rotors.
Fan, compressor and other gas turbine engine rotors may have a BLISK or a BLUM. BLISKS have blades that are integral with a disk and BLUMS have blades that are integral with a drum. Conventionally, BLISKS and BLUMS are made by machining an airfoil shape (using conventional machining or ECM/EDM processes) from a forged disk. Linear and angularly reciprocating friction welding methods have been under development for manufacturing BLISKS and BLUMS for gas turbine engine rotors. Angularly reciprocating friction welding includes the disc or drum rotor being angularly reciprocated while the airfoils or blades are pressed radially against the disk or rotor circumference. Linear reciprocating friction welding includes linear reciprocating airfoils or the blades as they are pressed radially against the disk or rotor circumference.
In friction welding, the disk is clamped, a blade is clamped in a reciprocating head of a machine, and the blade is rubbed against a surface of the disk in a reciprocating motion to generate frictional heat at an interface between the disk and the blade. When a predetermined loss of length is achieved, the blade is brought suddenly to a halt at a precisely defined location on the disk and is pressed against the disk for a short time to create the weld. When the blade and disk assembly has cooled flash at the interface is removed and any required machining operations are carried out.
One drawback to using BLISKS and BLUMS is the high manufacturing cost. The manufacturing processes described above are expensive and complex to perform on airfoil shapes, particularly, the complex shapes used today and being developed for future use. Additionally, the disk material and the airfoil material must meet different design requirements. Machining the blisk from one piece often requires compromises in the part design or material selection.
A method for manufacturing an integrally bladed rotor includes fixturing a plurality of blade blanks having radially inwardly facing blade conical surfaces in a segmented blade ring assembly circumscribed around an axis. A rotor ring is rotated to a contact speed. The rotor ring has a radially outwardly facing ring conical surface circumscribed around the axis and mates to the blade conical surfaces. The rotor ring and the segmented blade ring assembly are frictionally engaged under an axially applied weld load to effect a conical inertia weld therebetween along the mating blade conical surfaces and ring conical surface. In one embodiment, each of the blade blanks includes an airfoil portion extending radially outwardly from an annular base portion and the base portion includes the mating blade conical surfaces. The base portion includes a radially outer conical surface parallel to the blade conical surface and the conical inertia weld passes through the airfoil portion. Completed airfoils and radially outer flowpath surface are formed by machining excess stock from the base portion and the rotor ring after the welding. Materials of the blade blanks and the rotor ring may be two different alloys.
In another embodiment, each of the blade blanks includes a rim portion of the integrally bladed rotor and the conical inertia weld is between the rim portions and a conical rotor ring. Holes may be machined in an annular region of the rim. The holes may be circumferentially evenly distributed within the annular region and centered along radii passing through interfaces the blade blanks.
The invention includes the integrally bladed rotor and the airfoils circumferentially distributed about and integral with the rim. The airfoils extend radially outwardly from respective airfoil bases on a radially outer flowpath surface of the rim to airfoil tips. A conical inertia weld is located between the airfoil tips and a radially inwardly facing rim surface of the rim.